Kell antigen system

Human blood group system

Template:Infobox blood group system

The Kell antigen system is a group of antigens on the human red blood cell surface that are important in blood transfusion medicine. The system is named after the first patient in whom the antibodies were discovered. The Kell blood group system is the third most important blood group system after the ABO and Rh systems.

Structure and Genetics

The Kell antigen system is encoded by the KEL gene, which is located on chromosome 7. The KEL gene encodes a type II transmembrane glycoprotein that is expressed on the surface of red blood cells. The Kell protein is a zinc endopeptidase that is involved in the regulation of cell surface expression of other proteins.

The most clinically significant antigens in the Kell system are K (Kell) and k (Cellano). Other antigens include Kp^a, Kp^b, Js^a, and Js^b. The presence or absence of these antigens is determined by allelic variations in the KEL gene.

Clinical Significance

The Kell antigen system is highly immunogenic, meaning that it can provoke an immune response in individuals who lack the antigen. The most common and clinically significant antibody in the Kell system is anti-K, which can cause hemolytic transfusion reactions and hemolytic disease of the newborn (HDN).

Hemolytic Transfusion Reactions

When a person who lacks the Kell antigen (K-negative) receives blood from a donor who is K-positive, they may develop anti-K antibodies. If the person is subsequently transfused with K-positive blood, these antibodies can cause a hemolytic transfusion reaction, which is a serious and potentially life-threatening condition.

Hemolytic Disease of the Newborn

Anti-K antibodies can also cross the placenta during pregnancy and attack the red blood cells of a Kell-positive fetus, leading to hemolytic disease of the newborn. This condition can result in severe anemia, jaundice, and even fetal death if not properly managed.

Testing and Compatibility

Blood banks routinely test for Kell antigens and antibodies to ensure compatibility between donors and recipients. This is especially important for women of childbearing age to prevent HDN.

Also see

• ABO blood group system
• Rh blood group system
• Hemolytic disease of the newborn
• Blood transfusion